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Title:Survival and space use of riparian muskrats (Ondatra zibethicus) within an agroecosystem
Author(s):Ahlers, Adam A.
Advisor(s):Heske, Edward J.; Schooley, Robert L.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):home range
linear habitat
Ondatra zibethicus
predation risk
riparian zone
space use
Abstract:Increased agricultural production within the Grand Prairie region U.S.A. has resulted in drainage of most natural wetlands within the landscape. Semi-aquatic species that are associated with these habitats have shifted much of their distribution to riparian habitats that have unstable flow regimes and inundation times that could be related to position within watersheds. Muskrats (Ondatra zibethicus) are an economically important furbearer species in this region and occur in small streams and agricultural ditches throughout the Midwest. However, information regarding space use and survival of muskrats in these highly altered habitats is lacking. I examined predation risk, survival, home ranges, and space use of muskrats within small streams and agricultural ditches in a human-dominated agricultural landscape in east-central Illinois from 2007-2009. To evaluate predation risk of riparian muskrats, I monitored displacement times of radiomarked individuals during flooding events in relation to landscape position. I used known-fate models and an information-theoretic approach to examine effects of age, season, hydrology, and riparian width on weekly survival rates. As expected, muskrats positioned farther from headwaters were displaced longer, and exposed to predation from terrestrial predators longer, than those positioned closer to headwaters during flooding events. Contrary to my prediction, increased exposure during floods did not translate into lower survival because most mortalities were due to mink (Neovison vison) predation along stream edges during non-flooding periods. Muskrat weekly survival was lower in winter (0.9377, SE = 0.1793) than in non-winter (0.9770, SE = 0.0116) and positively related to riparian width. Larger riparian buffers were associated with greater muskrat survival in small streams and agricultural ditches within highly altered, human-dominated agroecosystems. To evaluate home ranges and space use of riparian muskrats, I monitored movements of radiomarked individuals occurring in small streams and agricultural ditches. I used an information-theoretic approach to determine the effects of age, hydrology, burrows, local vegetation and stream morphology on home-range size. Muskrat home ranges were highly linear and restricted to stream bank edges. Home-range size was influenced by age class and positively related to number of burrows used per individual. Adults had longer home ranges (804 m, SE = 171) than did juveniles (529 m, SE = 53), and home ranges of combined age classes averaged 582 m (SE = 56). Muskrats used an average of ~7 bank burrows (range = 3 – 13). An analysis of space use confirmed my hypothesis that muskrats are multiple central-place foragers that used space non-randomly within their home range. My study provides a rare example of linking riparian buffers to fitness for a stream-associated organism while also providing insights on how muskrats use space within restricted linear habitats.
Issue Date:2010-05-19
Rights Information:Copyright 2010 Adam A. Ahlers
Date Available in IDEALS:2010-05-19
Date Deposited:May 2010

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